In-vehicle communication system, relay device, and communication method

ABSTRACT

A relay device directly connected to end nodes in an in-vehicle network transmits a failure detection packet to each end node. When each end node can receive the failure detection packet, each end node transmits a response to the relay device. When the relay device receives the response, the relay device transmits another failure detection packet. The end node determines that the in-vehicle network is normal when the value of the previous failure detection packet does not match the value of the other failure detection packet, and determines that the in-vehicle network is not normal when the value of the previous failure detection packet matches the value of the other failure detection packet.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a continuation application of InternationalPatent Application No. PCT/JP2020/007946 filed on Feb. 27, 2020, whichdesignated the U.S. and claims the benefit of priority from JapanesePatent Application No. 2019-088609 filed on May 8, 2019. The entiredisclosures of all of the above applications are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to an in-vehicle communication system, arelay device, and a communication method.

BACKGROUND

A conceivable technique provides an in-vehicle network system in which aplurality of information processing devices mounted on a vehicle areconnected to a network such as a multiplex communication line. It isknown that an information processing device, which is an end node of anetwork system, determines a communication state between end nodes.Specifically, it is known that the communication status between endnodes is determined whether the end node can send an ICMP (InternetControl Message Protocol) Echo Request (hereinafter, echo request) toanother end node, and receive the response, i.e., ICMP Echo Reply(hereinafter, echo response).

SUMMARY

According to an example, a relay device directly connected to end nodesin an in-vehicle network transmits a failure detection packet to eachend node. When each end node can receive the failure detection packet,each end node transmits a response to the relay device. When the relaydevice receives the response, the relay device transmits another failuredetection packet. The end node determines that the in-vehicle network isnormal when the value of the previous failure detection packet does notmatch the value of the other failure detection packet, and determinesthat the in-vehicle network is not normal when the value of the previousfailure detection packet matches the value of the other failuredetection packet.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a diagram showing an example of a schematic configuration ofan in-vehicle communication system;

FIG. 2 is a diagram illustrating one example of a schematicconfiguration of a relay device;

FIG. 3 is a diagram showing an example of a data structure of an ICMPmessage;

FIG. 4 is a diagram showing an example of a schematic configuration ofan end node;

FIG. 5 is a flowchart showing an example of a flow ofdetermination-related processing on the relay device side in the relaydevice;

FIG. 6 is a sequence diagram showing an example of a flow of a statedetermination-related processing in the in-vehicle communication system;

FIG. 7 is a sequence diagram showing an example of a process flow fordetermining a communication state between end nodes in a conceivabletechnique;

FIG. 8 is a diagram for explaining an example of the effect of reducingthe number of required communication paths by the configuration of thefirst embodiment;

FIG. 9 is a diagram showing an example of a connection mode betweenrelay devices; and

FIG. 10 is a diagram showing an example of a schematic configuration ofan in-vehicle communication system.

DETAILED DESCRIPTION

Since the in-vehicle network system (hereinafter, in-vehicle network)handles signals related to vehicle control, it is required to determinethe communication state of the in-vehicle network more quickly. However,in the conceivable technique, when the communication state is determinedbetween the end nodes, the end nodes need to transmit and receivesignals four times. Specifically, the second end node receives the echorequest transmitted from the first end node, sends an echo response fromthe second end node to the first end node, and the first end node sendsthe echo request to the second end node, and the second end nodereceives the echo response transmitted from the first end node withrespect to the echo request, so that the transmission and reception areperformed four times.

In view of the above points, an in-vehicle communication system, a relaydevice, and a communication method are provided such that enable eachend node to determine the communication state of the in-vehicle networkmore quickly than that the end nodes can determine the communicationstate of the in-vehicle network to each other.

The in-vehicle communication system of the present embodiments includes:a plurality of end nodes as information processing devices included inthe in-vehicle network and used for a vehicle; and a relay devicedirectly connected to the plurality of end nodes. In the in-vehiclecommunication system including the above, the relay device includes: arequest transmitting unit for transmitting a failure detection packet,which is a packet for detecting the communication status, to each endnode; and a response receiving unit for receiving the response from theend node that can receive the failure detection packet. When theresponse receiving unit receives a response from an end node, therequest transmitting unit transmits another failure detection packethaving a different value from the previously transmitted failuredetection packet to the end node to which the previously transmittedfailure detection packet is received. The end node includes: a requestreceiving unit for receiving the fault detection packet transmitted fromthe relay device; a response transmitting unit for transmitting theresponse to the relay device when the request receiving unit can receivethe fault detection packet; and a communication status determinationunit for determining that the communication status of the in-vehiclenetwork is normal when the value of the previous failure detectionpacket received by the request receiving unit before the responsetransmitting unit transmits the response does not match the value of thecurrent failure detection packet received by the request receiving unitafter the response transmitting unit transmits the response, and fordetermining that the communication status of the in-vehicle network isabnormal when the value of the previous failure detection packet doesnot match the value of the current failure detection packet.

The communication method of the present embodiments includes:transmitting the failure detection packet, which is a packet fordetecting the communication status, to each end node by the relay devicedirectly connected to a plurality of end nodes as information processingdevices included in an in-vehicle network; transmitting the response tothe relay device by the end node when the end node can receive thefailure detection packet transmitted from the relay device; transmittinganother failure detection packet having the value different from thevalue of the previously transmitted failure detection packet to the endnode to which the relay device transmits the previously transmittedfailure detection packet when the relay device receives the responsefrom the end node; determining that the communication status of thein-vehicle network is normal when the value of the previous failuredetection packet received by the end node before the end node transmitsthe response does not match the value of the current failure detectionpacket received by the end node after the end node transmits theresponse; and determining that the communication status of thein-vehicle network is abnormal when the value of the previous failuredetection packet does not match the value of the current failuredetection packet.

According to these, when the relay device receives the response withrespect to the failure detection packet transmitted last time from theend node, the relay device sends the failure detection packet having adifferent value from the failure detection packet transmitted last timeto the end node to which the relay device sent the failure detectionpacket last time. Therefore, if there is no abnormality in thecommunication state with the relay device, the end node receives thefailure detection packet having a different value from the previouslyreceived failure detection packet. Thus, in the end node, when the valueof the previous failure detection packet received before sending theresponse does not match the value of the current failure detectionpacket received after sending the response, the end node determines thatthere is no abnormality in the communication status of the network. Whenthe values match, the end node determines that there is an abnormalityin the communication status of the in-vehicle network. Therefore, itbecomes possible to determine the communication state of the in-vehiclenetwork at the end node.

Since a plurality of end nodes are directly connected to the relaydevice, it is possible to determine the communication status of thein-vehicle network individually from each of the plurality of end nodes.In addition, the transmission and reception until the end nodedetermines the communication status of the in-vehicle network isperformed three times at most such as the reception of the failuredetection packet from the relay device, the transmission of the responseto the relay device, and the reception of the failure detection packethaving the value different from the value of the failure detectionpacket received last time from the relay device. Therefore, the numberof times is less than four times when the communication state of thein-vehicle network is determined between the end nodes. As a result, itbecomes possible to determine the communication status of the in-vehiclenetwork by individual end node more quickly than a case where thecommunication status of the in-vehicle network is determined between theend nodes.

The relay device of the present embodiments is used in a vehicle anddirectly connected to a plurality of end nodes as information processingdevices included in an in-vehicle network. The relay device includes: arequest transmission unit that transmits a failure detection packet,which is a packet for detecting a communication status, to an end node;and a response reception unit that receives a response transmitted fromthe end node that can receive the failure detection packet. When theresponse reception unit receives a response from the end node, therequest transmitting unit transmits the failure detection packet havinga different value from the previously transmitted failure detectionpacket to the end node to which the relay device previously transmitsthe failure detection packet.

According to these, when the relay device receives the response withrespect to the failure detection packet transmitted last time from theend node, the relay device sends the failure detection packet having adifferent value from the failure detection packet transmitted last timeto the end node to which the relay device sent the failure detectionpacket last time. Therefore, if there is no abnormality in thecommunication state with the relay device, the end node receives thefailure detection packet having a different value from the previouslyreceived failure detection packet. Therefore, at the end node, itbecomes possible to determine whether or not there is an abnormality inthe communication status of the in-vehicle network by checking whetherthe value of the previous failure detection packet received beforesending the response matches the value of the current failure detectionpacket received after sending the response. Since a plurality of endnodes are directly connected to the relay device, it is possible todetermine the communication status of the in-vehicle networkindividually from each of the plurality of end nodes. In addition, thetransmission and reception until the end node determines thecommunication status of the in-vehicle network is performed three timesat most such as the reception of the failure detection packet from therelay device, the transmission of the response to the relay device, andthe reception of the failure detection packet having the value differentfrom the value of the failure detection packet received last time fromthe relay device. Therefore, the number of times is less than four timeswhen the communication state of the in-vehicle network is determinedbetween the end nodes. As a result, it becomes possible to determine thecommunication status of the in-vehicle network by individual end nodemore quickly than a case where the communication status of thein-vehicle network is determined between the end nodes.

Multiple embodiments will be described for disclosure hereinafter withreference to the drawings. For convenience of description, the partshaving the same functions as the parts shown in the drawings used in thedescription up to that point in multiple embodiments may be designatedby the same reference numerals and the description thereof may beomitted. Description in another applicable embodiment may be referred tofor such a portion denoted by the identical reference sign.

Embodiment 1

<Outline Configuration of In-Vehicle Communication System 1>

The following will describe a first embodiment of the present disclosurewith reference to the accompanying drawings. First, the in-vehiclecommunication system 1 will be described with reference to FIG. 1. Thein-vehicle communication system 1 is mounted on a vehicle, and includesa plurality of relay devices 10 and a plurality of end nodes 20 as shownin FIG. 1.

The end node 20 is an information processing device used in a vehicle.An ECU is an example of the end node 20. In the following, a case wherethe end node 20 is an ECU will be described as an example. The end node20 includes a processor, a memory, I/O, and a bus connecting them. Theend node 20 exerts a function corresponding to the control program byexecuting the control program stored in the memory. The memory referredto here is a non-transitory tangible storage medium for storing programsand data that can be read by a computer non-transitory way. Thenon-transitory tangible storage medium is embodied by a semiconductormemory or a magnetic disk. The details of the end node 20 will bedescribed later.

The relay device 10 relays the communication between the end nodes 20.The relay device 10 is connected to the end node 20 and another relaydevice 10 by a communication line. The connection form between the relaydevices 10 may be any of a star type, a ring type, and a mesh type. Asshown in FIG. 1, the relay device 10 is directly connected to aplurality of end nodes 20. FIG. 1 shows an example in which two relaydevices 10 are directly connected to three end nodes 20 respectively.The communication network of the relay device 10 and the end node 20connected by the communication line corresponds to the in-vehiclenetwork. The example shown in FIG. 1 is merely an example, and thenumber of relay devices 10 included in the in-vehicle communicationsystem 1 may be three or more. Further, the number of end nodes 20directly connected to the relay device 10 may be a plurality other thantwo.

The relay device 10 includes a processor, a memory, I/O, and a busconnecting them. The relay device 10 exerts a function corresponding tothe control program by executing the control program stored in thememory. For example, the relay device 10 executes a process related tothe determination of the communication state of the in-vehicle network(hereinafter, the determination related process on the relay deviceside) by executing the control program. The memory referred to here is anon-transitory tangible storage medium for storing programs and datathat can be read by a computer non-transitory way. The non-transitorytangible storage medium is embodied by a semiconductor memory or amagnetic disk. The details of the relay device 10 will be describedbelow.

<Outline Configuration of Relay Device 10>

Subsequently, the schematic configuration of the relay device 10 will bedescribed with reference to FIG. 2. In FIG. 2, for convenience, theconfigurations other than those related to the determination-relatedprocess on the relay device side are not shown. The relay device 10includes a request transmission unit 101, a response reception unit 102,and a transmission control unit 103 as functional blocks. A part or allof the functions executed by the relay device 10 may be configured inhardware by one or multiple ICs or the like. A part or all of thefunctional blocks included in the relay device 10 may be realized by acombination of execution of software by a processor and hardwaremembers.

The request transmission unit 101 transmits a packet for detecting thecommunication status (hereinafter referred to as a failure detectionpacket) to the end node 20 which is directly connected by thecommunication line. In the following, a case where the in-vehiclecommunication system 1 provides ICMP (Internet Control MessageProtocol), which is an Internet control notification protocol, will bedescribed as an example. Therefore, in the following, the failuredetection packet will be described as an ICMP message (hereinafter,simply echo request) in which the type of the ICMP packet is an echorequest. This echo request corresponds to an echo request notification.As an example, the request transmission unit 101 may sequentiallytransmit echo requests to two end nodes 20 among a plurality of endnodes 20 directly connected to the relay device 10. Further, the requesttransmission unit 101 may sequentially transmit echo requests to aplurality of end nodes 20 directly connected to the relay device 10.

The data structure of the ICMP packet includes an IP header and an ICMPmessage. As shown in FIG. 3, the ICMP message includes fields such as“type”, “code”, “checksum”, “ID”, “sequence number”, and “data”. The“Type” is the value of the function type of the ICMP message. The “ID”is a value arbitrarily set by the transmission source. The “sequencenumber” is a serial number when repeatedly transmitting packets with thesame ID. The “Data” corresponds to the payload.

The response receiving unit 102 receives the response transmitted fromthe end node 20 that has been able to receive the echo requesttransmitted from the request transmitting unit 101. This response is anICMP message (hereinafter, simply echo response) in which the type ofthe ICMP packet is an echo response. This echo response corresponds toan echo response notification.

The transmission control unit 103 controls the transmission of the echorequest from the request transmission unit 101. The transmission controlunit 103 may sequentially transmit echo requests from the requesttransmission unit 101 to the plurality of end nodes 20 at predeterminedtimings such as periodical times. Further, when the response receivingunit 102 receives the echo response from the end node 20, thetransmission control unit 103 controls the request transmitting unit 101to send an echo request, having a value different from the echo requestpreviously transmitted to the end node 20, to the end node 20. As aresult, when the response receiving unit 102 receives the echo responsefrom the end node 20, the request transmitting unit 101 sends an echorequest, having a value different from that of the echo requestpreviously transmitted to the end node 20, to the end node 20.

The value different from the echo request transmitted last time may be,for example, the value of the payload in the ICMP packet. The value ofthe payload may be the payload length or the like, alternatively, may bethe value of the binary data in the “data” field. In addition to thepayload value, the ID value and the sequence number value in the ICMPmessage may be used. When the payload value is used, it is possible toswitch the echo request value depending on whether or not the echoresponse is received without changing the ID.

<Outline Configuration of End Node 20>

Subsequently, the schematic configuration of the end node 20 will bedescribed with reference to FIG. 4. In FIG. 4, for convenience,configurations other than those related to the processing related to thedetermination of the communication state of the in-vehicle network arenot shown. The end node 20 includes a request reception unit 201, aresponse transmission unit 202, a transmission control unit 203, and acommunication state determination unit 204 as functional blocks. A partor all of the functions executed by the end node 20 may be configured inhardware by one or multiple ICs or the like. A part or all of thefunctional blocks included in the relay device 10 may be realized by acombination of execution of software by a processor and hardwaremembers.

The request receiving unit 201 receives the echo request transmittedfrom the relay device 10. The request receiving unit 201 receives theecho request when the echo request is transmitted from the relay device10. When the request receiving unit 201 can receive the echo request,the response transmitting unit 202 transmits the echo response to therelay device 10 which is directly connected thereto.

The transmission control unit 203 controls the transmission of the echoresponse from the response transmission unit 202. When the requestreceiving unit 201 can receive the echo request transmitted from therelay device 10, the transmission control unit 203 causes the responsetransmission unit 202 to transmit the echo response to the relay device10.

The communication state determination unit 204 determines whether or notthere is an abnormality in the communication state of the in-vehiclenetwork. As an example, the communication state determination unit 204may determine the communication state between the relay device 10directly connected to its own end node 20 and its own end node 20 as thecommunication state of the in-vehicle network.

The communication state determination unit 204 determines that there isno abnormality in the communication status of the in-vehicle networkwhen the value of the previous echo request received by the requestreceiving unit 201 before the response transmitting unit 202 transmitsthe echo response does not match the value of the current echo requestreceived by the request receiving unit 201 after the responsetransmitting unit 202 transmits the echo response. On the other hand,when the values for these packets match, it is determined that there isan abnormality in the communication status of the in-vehicle network.

<Determination Related Processing on the Relay Device Side in the RelayDevice 10>

Here, an example of the flow of the relay device-sidedetermination-related processing in the relay device 10 will bedescribed with reference to the flowchart of FIG. 5. The flowchart ofFIG. 5 may be configured to start periodically, for example. theexecution of the steps included in the relay device-sidedetermination-related processing corresponds to the execution of thecommunication method.

First, in step S1, the request transmission unit 101 transmits an echorequest to the end node 20 which is directly connected by thecommunication line. The echo request at this time is defined as reqA. Asan example, the request transmission unit 101 may sequentially transmitecho requests reqA to two end nodes 20 among a plurality of end nodes 20directly connected to the relay device 10.

In step S2, when the response receiving unit 102 receives the echoresponse from the end node 20 (i.e., YES in S2), the process proceeds tostep S4. On the other hand, when the response receiving unit 102 doesnot receive the echo response from the end node 20 (i.e., NO in S2), theprocess proceeds to step S3.

In step S3, when the elapsed time from transmitting the echo requestreqA to the end node 20 has reached the set time (i.e., YES in S3), theprocess proceeds to step S5. The elapsed time may be measured by thetimer circuit. The set time can be predetermined arbitrarily. On theother hand, when the time is not up (i.e., NO in S3), the processreturns to S2 and the process is repeated.

In step S4, the transmission control unit 103 controls the requesttransmission unit 101 to send the echo request, having a value differentfrom the echo request reqA previously transmitted to the end node 20, tothe end node 20 that received the echo response in S2. An echo requesthaving a value different from that of the echo request reqA is referredto as reqB.

In step S5, in the case of the end timing of the relay device sidedetermination-related processing (i.e., YES in S5), the relaydevice-side determination-related processing is terminated. On the otherhand, when it is not the end timing of the relay device sidedetermination-related processing (i.e., NO in S5), the process returnsto S2 and the processing is repeated. As an example of the end timing ofthe determination-related processing on the relay device side, there isa case where the echo request reqB is transmitted in S4 to all ofmultiple end nodes 20 to which the echo request reqA is transmitted atS1, or a case where NO is set in S3. When it is not the end timing ofthe determination related processing on the relay device side, theprocessing is repeated until the echo request reqB is transmitted in S4to all of multiple end nodes 20 to which the echo request reqA istransmitted at S1, or NO is set in S3.

The relay device side determination-related processing may be configuredsuch that the above described processing is sequentially performed forall the combinations by changing the combination of two end nodes 20among the plurality of end nodes 20 directly connected to the relaydevice 10. Further, the relay device side determination-relatedprocessing may be configured such that the echo request reqA issequentially transmitted in S1 for all the end nodes 20 directlyconnected to the relay device 10 and the subsequent processing isperformed.

<State Determination Related Processing in In-Vehicle CommunicationSystem 1>

Subsequently, an example of the flow of the process related to thedetermination of the communication state of the in-vehicle network inthe in-vehicle communication system 1 (hereinafter, the statedetermination-related process) will be described with reference to thesequence diagram of FIG. 6. In the example of FIG. 6, two end nodes 20among the plurality of end nodes 20 will be described as the first endnode 21 and the second end node 22. In the example of FIG. 6, an exampleof the processing flow when there is no abnormality in the communicationstate between the relay device 10 and the first end node 21 and thesecond end node 22 is shown. In the example of FIG. 6, for convenience,the description will be limited to the combination of the first end node21 and the second end node 22 among the plurality of end nodes 20.

First, at t1, the relay device 10 sequentially transmits the echorequest reqA to the first end node 21 and the second end node 22. At t2and t3, the first end node 21 and the second end node 22 each receivethe echo request reqA transmitted from the relay device 10. At t4 andt5, the first end node 21 and the second end node 22 each transmit anecho response reply to the relay device 10.

At t6, the relay device 10 receives the echo response reply transmittedfrom the first end node 21 and the second end node 22, respectively. Att7, the relay device 10 sequentially transmits the echo request reqBhaving a value different from the echo request reqA transmitted lasttime to the first end node 21 and the second end node 22.

At t8 and t9, the first end node 21 and the second end node 22 eachreceive the echo request reqB transmitted from the relay device 10. Att10 and t11, each of the first end node 21 and the second end node 22compares the echo request reqA received last time with the echo requestreqB received the present time, respectively. Then, since the echorequest reqA received last time and the echo request reqB received thepresent time do not match, it is determined that there is no abnormalityin the communication state with the relay device 10. The feature thatthere is no abnormality in the communication state with the relay device10 as used herein means that information can be transmitted to the relaydevice 10 and information can be received from the relay device 10.

At t12 and t13, the first end node 21 and the second end node 22 eachtransmit an echo response reply to the relay device 10. At t14, therelay device 10 receives the echo response reply transmitted from thefirst end node 21 and the second end node 22, respectively. At t15, therelay device 10 sequentially transmits the echo request reqC having avalue different from the echo request reqB transmitted last time to thefirst end node 21 and the second end node 22.

At t16 and t17, the first end node 21 and the second end node 22 eachreceive the echo request reqC transmitted from the relay device 10. Att18 and t19, each of the first end node 21 and the second end node 22compares the echo request reqB received last time with the echo requestreqC received the present time, respectively. Then, since the echorequest reqB received last time and the echo request reqC received thepresent time do not match, it is determined that there is no abnormalityin the communication state with the relay device 10.

As shown in FIG. 6, in the in-vehicle communication system 1, it ispossible to perform three transmissions/receptions of t3, t5, and t9 forthe first time before the first end node 21 determines the communicationstate of the in-vehicle network. Further, from the second time andsubsequent times, it is possible to complete the transmission andreception twice at t13 and t17. By the time the second end node 22determines the communication state of the in-vehicle network, thetransmission/reception of three times at t2, t4, and t8 for the firstdetermination time can be completed. Further, from the seconddetermination time and subsequent determination times, it is possible tocomplete the transmission and reception twice at t12 and t16. This is asmaller number of transmissions/receptions as compared with theconceivable technique of determining the communication status betweenend nodes. Hereinafter, an example of processing for determining thecommunication state of the in-vehicle network in this conceivabletechnique will be described.

<Communication Determination Processing Using Conceivable Technique>

Subsequently, an example of the process flow of determining thecommunication state of the in-vehicle network in the conceivabletechnique for determining the communication state between the end nodeswill be described with reference to the sequence diagram of FIG. 7. Inthe example of FIG. 7, an example in which the end node B determines thecommunication state with the end node A is shown. In the example of FIG.7, an example of the processing flow when there is no abnormality in thecommunication state between the end node A and the end node B is shown.

First, at t101, the end node A transmits an echo request req to the endnode B. At t102, the end node B receives the echo request reqtransmitted from the end node A. At t103, the end node B transmits anecho response reply to the end node A. At t104, the end node A receivesthe echo response reply transmitted from the end node B.

At t105, the end node B transmits an echo request req to the end node A.At t106, the end node A receives the echo request req transmitted fromthe end node B. At t107, the end node A transmits an echo response tothe end node B. At t108, the end node B receives the echo responsetransmitted from the end node A. At t109, the end node B determines thatthere is no abnormality in the communication state with the end node Abased on the feature that the end node B can receive the echo requestand the echo response from the end node A.

As shown in FIG. 7, in the conceivable technique, fourtransmissions/receptions at t102, t103, t105, and t108 are requiredbefore the end node B determines the communication state of thein-vehicle network. Therefore, in the in-vehicle communication system 1,the number of transmissions and receptions until the communication stateof the in-vehicle network is determined is smaller than that in theconceivable technique.

<Summary of Embodiment 1>

According to the configuration of the first embodiment, as describedabove, the number of transmissions/receptions until one end node 20determines the communication state of the in-vehicle network is lessthan the number of transmissions/receptions until the end nodesdetermine the communication status of the in-vehicle network to eachother. As a result, it becomes possible to determine the communicationstatus of the in-vehicle network by individual end node more quicklythan a case where the communication status of the in-vehicle network isdetermined between the end nodes. By making it possible to determine thecommunication status of the end node more quickly, it is possible toself-recover the end node more quickly in the event of an abnormality.For example, an example of self-recovery includes restarting.

Further, when the communication state of the in-vehicle network isdetermined between the end nodes, an increase in the number ofcommunication paths required for determining the communication statebecomes a difficulty. On the other hand, according to the configurationof the first embodiment, each of the plurality of relay devices 10 isdirectly connected to the plurality of end nodes 20, and each of the endnodes 20 determines the communication state of the in-vehicle networkwith the relay device 10. Therefore, it is possible to suppress thenumber of communication paths required to determine the communicationstatus of the in-vehicle network.

Here, an example of the effect of reducing the number of requiredcommunication paths by the configuration of the first embodiment will bedescribed with reference to FIG. 8. FIG. 8 shows the number of routesrequired in the in-vehicle communication system 1 and the number ofroutes required in the conceivable technique with respect to thecombination of the number of relay devices 10 and the number of endnodes 20. In the example of FIG. 8, a case where three end nodes 20 aredirectly connected to one relay device 10 respectively will be describedas an example.

The required number of routes in the in-vehicle communication system 1is obtained by adding up the number of routes between the relay device10 and the end nodes 20 and the number of routes between the relaydevices 10. On the other hand, the required number of routes in theconceivable technique can be obtained from the number of routes betweenthe end nodes 20. Therefore, for example, in the case where the numberof relay devices 10 is four and the number of end nodes 20 is 12, therequired number of routes in the in-vehicle communication system 1 canbe obtained by calculating an equation of 3×4+₄C₂ (that is, 2 ofcombination 4). On the other hand, the required number of routes in theconceivable technique can be obtained by calculating ₁₂C₂ (that is, 2 ofcombination 12). The required number of routes is the same valueregardless of the connection form between the relay devices 10 such asthe star type, the ring type, and the mesh type shown in FIG. 9. Thesquare in FIG. 9 indicates the relay device 10, and the circle indicatesthe end node 20.

As shown in FIG. 8, when there are two relay devices 10 and six endnodes 20, the required number of routes in the in-vehicle communicationsystem 1 is 4, and the required number of routes in the conceivabletechnique is 15. When there are three relay devices 10 and nine endnodes 20, the number of required routes in the in-vehicle communicationsystem 1 is 11, and the number of required routes in the conceivabletechnique is 36. When there are four relay devices 10 and twelve endnodes 20, the number of required routes in the in-vehicle communicationsystem 1 is 18, and the number of required routes in the conceivabletechnique is 66. When the relay device 10 is 10 and the end node 20 is30, the required number of routes in the in-vehicle communication system1 is 75, and the required number of routes in the conceivable techniqueis 435. As described above, according to the configuration of the firstembodiment, it is possible to reduce the number of required routes ascompared with the case where the communication state of the in-vehiclenetwork is determined between the end nodes.

Second Embodiment

In the first embodiment, a configuration in which a plurality of relaydevices 10 are included in the in-vehicle communication system 1 isshown, but the present embodiment may not be necessarily limited tothis. For example, as shown in FIG. 10, the in-vehicle communicationsystem 1 a may include only one relay device 10 (hereinafter, accordingto the second embodiment).

As shown in FIG. 10, the in-vehicle communication system 1 a includesone relay device 10 and a plurality of end nodes 20. The in-vehiclecommunication system 1 a is similar to the in-vehicle communicationsystem 1 of the first embodiment, except that the number of relaydevices 10 included is different. FIG. 10 shows an example in which onerelay device 10 is directly connected to four end nodes 20 respectively.

Since the configuration of the second embodiment is similar to that ofthe first embodiment except for the number of relay devices 10, thenumber of transmissions and receptions at the end node 20 until thecommunication state of the in-vehicle network is determined is less thana case of determining the communication status of the in-vehicle networkbetween end nodes, as in the first embodiment. As a result, it becomespossible to determine the communication status of the in-vehicle networkby individual end node more quickly than a case where the communicationstatus of the in-vehicle network is determined between the end nodes.

Further, in order to reduce the number of communication paths (that is,the required number of routes) required for determining thecommunication status of the in-vehicle network as compared with the casewhere the end nodes determine the communication status of the in-vehiclenetwork to each other, the number of end nodes 20 directly connected tothe relay device 10 may be preferably 4 or more. When the number of endnodes 20 directly connected to the relay device 10 is 4 or more, thenumber of required routes can be reduced as compared with the case wherethe end nodes determine the communication state of the in-vehiclenetwork to each other.

The controller and the method thereof described in the presentdisclosure are implemented by a dedicated computer provided byconfiguring a processor and a memory programmed to execute one or morefunctions embodied by a computer program. Alternatively, the controllerand the method described in the present disclosure may be implemented bya dedicated computer provided by configuring a processor with one ormore dedicated hardware logic circuits. Alternatively, the controllerand the method thereof described in the present disclosure are based ona combination of a processor and a memory programmed to execute one ormore functions and a processor configured by one or more hardware logiccircuits. It may be implemented by one or more configured dedicatedcomputers. The computer programs may be stored, as instructions to beexecuted by a computer, in a tangible non-transitory computer-readablestorage medium.

Here, the process of the flowchart or the flowchart described in thisapplication includes a plurality of sections (or steps), and eachsection is expressed as, for example, S1. Further, each section may bedivided into several subsections, while several sections may be combinedinto one section. Furthermore, each section thus configured may bereferred to as a device, module, or means.

Although the present disclosure has been described in accordance withembodiments, it is understood that the present disclosure is not limitedto such embodiments or structures. The present disclosure alsoencompasses various modified examples and modifications within a uniformrange. In addition, various combinations and forms, and further, othercombinations and forms including only one element, or more or less thanthese elements are also within the spirit and the scope of the presentdisclosure.

What is claimed is:
 1. An in-vehicle communication system for a vehiclecomprising: a plurality of end nodes as information processing devicesdisposed in an in-vehicle network; and at least one relay devicedirectly connected to the plurality of end nodes, wherein: the at leastone relay device includes: a request transmission unit that transmits afailure detection packet, which is a packet for detecting acommunication status, to each end node; and a response reception unitthat receives a response transmitted from at least one of the end nodescapable of receiving the failure detection packet; when the responsereception unit receives the response from the at least one of the endnodes, the request transmission unit transmits an other failuredetection packet, having a value different from a value of a previousfailure detection packet previously transmitted, to the at least one ofthe end nodes to which the previous failure detection packet ispreviously transmitted; each end node includes: a request reception unitthat receives the failure detection packet transmitted from the at leastone relay device; a response transmission unit that transmits theresponse to the at least one relay device when the request receptionunit can receive the failure detection packet; and a communication statedetermination unit that determines that a communication status of thein-vehicle network is normal when the value of the previous failuredetection packet received by the request reception unit before theresponse transmission unit transmits the response does not match thevalue of the other failure detection packet currently received by therequest transmission unit after the response transmission unit transmitsthe response, and determines that the communication status of thein-vehicle network is not normal when the value of the previous failuredetection packet matches the value of the other failure detectionpacket.
 2. The in-vehicle communication system according to claim 1,wherein: the at least one relay device is directly connected to four ormore of the end nodes.
 3. The in-vehicle communication system accordingto claim 1, wherein: the at least one relay device includes a pluralityof relay devices; and each relay device is directly connected to atleast a part of the plurality of end nodes.
 4. The in-vehiclecommunication system according to claim 1, wherein: the value of eachfailure detection packet is a value of a payload in the failuredetection packet; and when the response reception unit receives theresponse from the end node, the request transmission unit transmits theother failure detection packet having the value of the payload differentfrom the previous failure detection packet previously transmitted. 5.The in-vehicle communication system according to claim 1, wherein: theprevious failure detection packet and the other failure detection packetare echo request notifications among notifications related to anInternet control notification protocol; and the response is an echoresponse notification among the notifications related to the Internetcontrol notification protocol.
 6. A relay device for a vehicle directlyconnected to a plurality of end nodes as information processing devicesincluded in an in-vehicle network, the relay device comprising: arequest transmission unit that transmits a failure detection packet,which is a packet for detecting a communication status, to each endnode; and a response reception unit that receives a response transmittedfrom at least one of the end nodes capable of receiving the failuredetection packet, wherein: when the response reception unit receives theresponse from the at least one of the end nodes, the requesttransmission unit transmits an other failure detection packet, having avalue different from a value of a previous failure detection packetpreviously transmitted, to the at least one of the end nodes to whichthe previous failure detection packet is previously transmitted.
 7. Acommunication method comprising: transmitting a failure detectionpacket, which is a packet for detecting a communication status, to eachof a plurality of end nodes by a relay device directly connected to theplurality of end nodes as information processing devices included in anin-vehicle network; transmitting a response to the relay device by eachof the end nodes when each of the end nodes receives the failuredetection packet transmitted from the relay device; transmitting another failure detection packet, having a value different from a value ofa previous failure detection packet previously transmitted, by the relaydevice to at least one of the end nodes to which the previous failuredetection packet is previously transmitted when the relay devicereceives the response from the at least one of the end nodes;determining by the at least one of the end nodes that the communicationstatus of the in-vehicle network is normal when the value of theprevious failure detection packet received before transmitting theresponse does not match the value of the other failure detection packetcurrently received after transmitting the response; and determining bythe at least one of the end nodes that the communication status of thein-vehicle network is not normal when the value of the previous failuredetection packet matches the value of the other failure detectionpacket.
 8. The in-vehicle communication system according to claim 1,wherein: the at least one relay device further includes: one or moreprocessors; and a memory coupled to the one or more processors andstoring program instructions that when executed by the one or moreprocessors cause the one or more processors to provide at least: therequest transmission unit; and the response reception unit; and each endnode further includes: one or more processors; and a memory coupled tothe one or more processors and storing program instructions that whenexecuted by the one or more processors cause the one or more processorsto provide at least: the request reception unit; the responsetransmission unit; and the communication state determination unit. 9.The relay device according to claim 6, further comprising: one or moreprocessors; and a memory coupled to the one or more processors andstoring program instructions that when executed by the one or moreprocessors cause the one or more processors to provide at least: therequest transmission unit; and the response reception unit.